Understanding Thin Film Interference

In summary, white light is being sent through a thin film sandwiched between two materials with different indexes of refraction. The film thickness is 5.4 10-7 m and there is a phase shift when the light transitions from a medium with a lower index of refraction to one with a higher index of refraction.
  • #1
jwxie
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Homework Statement




White light is sent downward onto a horizontal thin film that is sandwiched between two materials. The indexes of refraction are 1.80 for the top material, 1.66 for the thin film, and 1.50 for the bottom material. The film thickness is 5.4 10-7 m.


Homework Equations



The Attempt at a Solution



From air to 1.80 (top), we have a phase shift of pi. From 1.80 to 1.66, we don't have phase shift, right?

From 1.66 to 1.50, do we have phase shift? Do we look at the phase shift based on n_f (index of refraction of the film) vs n?
If 1.66 is greater than 1.50 then we have a phase shift?
 

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  • #2
can anyone please verify my "claim?

Thank you! sorry for the bump!
 
  • #3
You get a phase shift for the reflection whenever you transition from a medium with a lower index of refraction to one of higher index of refraction.
 

1. What is the concept of interference in thin film?

The concept of interference in thin film refers to the phenomenon where light waves reflect off of the top and bottom surfaces of a thin film, causing them to interfere with each other. This results in certain wavelengths of light being amplified or canceled out, leading to the appearance of different colors in the film.

2. How does the thickness of the thin film affect interference?

The thickness of the thin film is directly related to the amount of interference that occurs. Thicker films will produce more pronounced interference patterns, while thinner films will have a more subtle effect on light waves. This is due to the fact that thicker films allow for more reflection and thus more opportunities for interference to occur.

3. What is the difference between constructive and destructive interference in thin film?

Constructive interference in thin film occurs when the light waves reflected off of the top and bottom surfaces are in phase, resulting in a brighter or more intense color. Destructive interference, on the other hand, occurs when the light waves are out of phase and cancel each other out, resulting in a darker or muted color.

4. How does the refractive index of the thin film and surrounding medium impact interference?

The refractive index of the thin film and surrounding medium plays a crucial role in interference. The larger the difference in refractive index between the two, the greater the amount of interference that will occur. This is because a larger difference in refractive index causes a larger phase shift in the light waves, leading to more pronounced interference patterns.

5. What are some practical applications of interference in thin film?

Interference in thin film has numerous practical applications, such as in anti-reflective coatings for glasses and camera lenses, color filters in LCD displays, and coatings on solar panels for improved light absorption. It also plays a role in determining the color of certain natural phenomena, such as the iridescent colors seen in soap bubbles and oil slicks.

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